An assumable mortgage lets a buyer take over the seller's existing loan at the seller's original rate — a decisive advantage when that rate sits far below today's market. This calculator prices that advantage: the monthly gap versus a new loan, the lifetime savings, and the cash gap the buyer still has to close.
The cash gap is the number that trips up most buyers: you cannot assume the loan and pay the seller the full price, because the loan only covers the balance. The difference must come from cash or a second lien at market rates.
| Scenario | Payment @ Existing | Payment @ Market | Monthly Gap | Lifetime Savings | Cash Gap |
|---|---|---|---|---|---|
| $520K price, 2.875% assumable, 26 yrs left, $310K balance | $1,412 | $2,110 | $699 | $217,946 | $210,000 |
| $650K price, 3.25% assumable, 28 yrs left, $400K balance | $1,815 | $2,692 | $877 | $294,825 | $250,000 |
| $380K price, 4.0% assumable, 24 yrs left, $260K balance | $1,406 | $1,785 | $379 | $109,214 | $120,000 |
| $750K price, 2.5% assumable, 27 yrs left, $500K balance | $2,124 | $3,439 | $1,315 | $426,167 | $250,000 |
| $420K price, 5.75% assumable, 25 yrs left, $300K balance | $1,887 | $2,026 | $138 | $41,491 | $120,000 |
Notice how the advantage grows as the gap between the existing rate and market rate widens. At 2.5% assumed against a 7.0% market rate the buyer's lifetime savings run to roughly $426,000 — which is exactly why sellers with low-rate loans can command a premium price on assumptions. At 5.75% against 6.5%, by contrast, the advantage is only about $41,000, barely enough to justify the time cost of an assumption.
This is the single most important practical point, and it is where most online discussions get vague. Assumability is a property of the loan program, not a negotiation you can talk your way into.
| Loan Type | Assumable? | What to know |
|---|---|---|
| FHA | Yes — by statute | FHA loans are assumable for both owner-occupants and, since 1989 changes, investors (with restrictions). Creditworthiness review applies to most new assumptions. |
| VA | Yes | Strongly assumable and widely used. Crucially, the seller's VA entitlement can stay tied up — a real risk they must understand. |
| USDA | Yes | Assumable with USDA approval; income limits for the area still apply to the incoming buyer. |
| Conventional | Usually no | Almost all conventional mortgages contain a due-on-sale clause. Fannie/Freddie allow assumptions only in narrow cases (e.g., certain family transfers). |
| Jumbo / portfolio | Case by case | Some portfolio lenders allow it with full underwriting; most do not. |
First, the equity gap. If the home sells for $520,000 and the assumable balance is $310,000, the buyer owes the seller $210,000 in cash or via a second mortgage — and second liens on an assumption typically price near market rates, which erodes part of the benefit. Second, the assumption fee and processing time. FHA and VA assumptions are handled by the servicer and can take 60 to 120 days, far longer than a normal closing, and many servicers charge a fee of several hundred to a few thousand dollars.
A seller with a 2.875% loan sitting on a home the market wants to price at 6.75% financing is offering something genuinely scarce. That scarcity can support a higher asking price. But for VA sellers, the remaining entitlement is consumed until the assumed loan is paid off — if the buyer later defaults, the seller's entitlement is at risk. VA sellers should always confirm with a lender whether they want a release of liability.
When a seller's loan carries a 3% rate and the market is at 6.75%, the assumable mortgage is not just a convenience — it is an asset with a calculable dollar value. That value is the present value of the payment difference over the loan's remaining life, less fees and less the cost of financing the equity gap.
In practice, this is why low-rate assumable loans sell at a premium and why some sellers advertise "assumable 2.875%" prominently. A buyer who can fund the equity gap in cash captures the full benefit; a buyer who must finance it with a second lien at 9%–12% captures less. Run both sides through the calculator before agreeing to a price — the headline rate can look far better than the fully-financed reality.
One caution on the lifetime savings figure: it assumes both loans run to full term. Most homeowners sell or refinance long before that. If you expect to move in five years, the relevant comparison is the monthly advantage over 60 payments, not the full-term number.
⚠️ Disclaimer: Assumability rules depend on the specific loan program, the servicer, and current FHA/VA/USDA guidance, which changes. Figures here are estimates of economic value, not a guarantee of eligibility or terms. Confirm assumability, fees, processing time, and the equity-gap financing plan with the loan servicer and a qualified lender before making an offer. This is not financial or legal advice.